The Behaviour of An Arrow Shot from a Compound Archery Bow

Abstract

The behaviour of an arrow exiting an archery bow is of interest in relation to equipment selection and optimization, as well as to the performance of the arrow down-range. In particular, it is a necessary input into a study of the impact of archer technique errors and wind drift. While the performances of recurve archery bows have been modelled by a number of researchers, those of compound archery bows have not. A compound archery bow is mechanically more complex and the archer holds the string using a mechanical release device rather than with fingers directly on the string. Consequently the arrow behaviour is significantly different from that for a recurve bow. This paper provides the results of an analysis of an arrow leaving a compound bow in both the vertical and the horizontal planes. Techniques similar to those used by Kooi for a recurve bow were used, together with photographs obtained using a triggered flash light. The paths taken by the bow's nocking point in both the vertical and the horizontal planes had a substantial influence on the arrow behaviour. In the vertical plane this was both measured and modelled for one bow type and for a second bow type it was modelled. In the horizontal plane it was measured and modelled for one bow type but with the locus varied by twisting the bow laterally. Three sizes of the most commonly used arrows were examined: the recommended size, and arrows one and two sizes stiffer. It was concluded that both the recommended size and the stiffer sizes behaved similarly, giving increased scope to optimize arrow selection for parameters such as wind drift. One major archer technique error, namely twisting the bow, was included in the analysis and shown to have a significant impact on the arrow behaviour and the path taken by the arrow in the horizontal plane.